Imagine a typical PGA par-4 hole that's 520 yards. The very best woman may hit 270 with the driver off the tee. That's barely halfway to the hole; there's 250 yards to go. Assuming a fairway shot, she can use a 3 wood and get another 200, 220 yards with a good strike. That leaves her 30 yards to the hole, meaning she'll be using a wedge to approach and then a possible putt for par.
The top 25 men on the PGA tour mostly average 300+ off the tee, with the best averaging over 310. Hit 300 off the tee on the 520 and you've got 220 to the hole, which a man can do with a 5 wood or a hybrid (or possibly a long iron). That can put him on the green in 2, putting for birdie.
So in this hypothetical average hole, the woman has basically zero chance for a birdie, whereas a man can be on the green putting for birdie in two strokes.
Now for a real world comparison: the 2014 US Open. The men's course was 7,562 yards and the winner (Martin Kaymer) finished in 271 strokes. The women's course was 6,649 yards (almost 100 yards shorter) and the winner (Michelle Wie) finished in 278 strokes. The women's course had par-4s as short as 330 yards, while the shorters par-4 on the men's course was 402.
The average hole on the men's tour is probably around 410 yards. The average on the women's tour is probably around 350.